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How It Works

Fluorouracil interferes with how cancer cells grow and divide. It affects all areas of the cell cycle.

Fluorouracil is an intravenous (IV) medicine. It usually is given according to a schedule, such as once a week or once every 3 to 4 weeks, but it may also be given continuously over 4 to 5 days. It also is available as a cream for the treatment of skin cancer.

Why It Is Used

Fluorouracil is used to treat many different types of cancer, such as cancer of the colon, rectum, breast, stomach, and pancreas. It may also be used to treat skin cancer.

How Well It Works

Fluorouracil is an effective cancer treatment. But the type of cancer you have and how widespread it is in your body affect how well this medicine slows or stops cancer growth.

Side Effects

Fluorouracil can cause many side effects. How severe the side effects are depends on how often you are treated and how large a dose of this medicine you receive. Common side effects include:

  • Mouth sores, a sore throat, and trouble swallowing.
  • Diarrhea and stomach pain.
  • Decreased white blood cell counts. Red blood cell counts and platelet counts can also be reduced.
  • Sun sensitivity and easy sunburning. Be sure to wear hats and sunscreen with a sun protection factor (SPF) of 30, and stay out of the sun as much as possible.
  • Watery eyes.
  • Darkening of nail beds.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Fluorouracil should be given only under the supervision of a medical oncologist.

Fluorouracil is used to treat many types of cancer. But how well the medicine works depends on the type of cancer and how widespread it is.

Fluorouracil is often given with another medicine called leucovorin. This can increase your chance of severe side effects.

Fluorouracil can cause birth defects. Do not use this medicine if you are pregnant or wish to become pregnant or father a child while you are taking it.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.


By Healthwise Staff
Primary Medical Reviewer Joy Melnikow, MD, MPH - Family Medicine
Specialist Medical Reviewer Douglas A. Stewart, MD - Medical Oncology
Last Revised October 26, 2009

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.